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GI Physiology > 5.8 Overview of the Large Intestine, Rectum, and Anal Canal > Flashcards

5.8 Overview of the Large Intestine, Rectum, and Anal Canal Flashcards

1
Q

What are the Parts of the Large Intestine?

A
  1. The Ileocaecal Valve (Sphincter)
  2. The Caecum
  3. The Appendix
  4. The Ascending Colon
  5. The Transverse Colon
  6. The Descending Colon
  7. The Sigmoid Colon
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2
Q

What follows the Sigmoid Colon?

A
  1. The Rectum

2. The Anal Canal

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3
Q

What is the Ileocaecal Valve?

A

The Sphincter between the Ileum and the Caecum

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4
Q

What is the Caecum?

A

A Blind Sac which leads into the Ascending Colon

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5
Q

What is the Appendix?

A

An attachment to the Caecum, with no known function, but is a common site of infection (Appendicitis)

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6
Q

What is the Ascending Colon?

A
  1. The 1st Part of the Colon
  2. It lies on the Right Side of the Abdomen, lateral to the Small Intestines
  3. It is Retroperitoneal
  4. It leads to the Transverse Colon
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7
Q

What is the Transverse Colon?

A
  1. The 2nd Part of the Colon
  2. It lies Superiorly to the to the Small Intestines.
  3. It is Intraperitoneal
  4. It leads to the Descending Colon
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8
Q

What is the Descending Colon?

A
  1. The 3rd Part of the Colon
  2. It lies on the Left Side of the Abdomen, lateral to the Small Intestines
  3. It is Retroperitoneal
  4. It leads to the Sigmoid Colon
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9
Q

What is the Sigmoid Colon?

A
  1. It is the Final Part of the Colon
  2. It lies on the Left Side of the Abdomen, Infero-laterally to the Small Intestines
  3. It is Intraperitoneal
  4. It leads to the Rectum
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10
Q

What is the Rectum?

A
  1. It is a Straight Muscular Tube between the Sigmoid Colon and the Anal Canal
  2. It has a Simple Columnar Epithelium (Mucosa)
  3. It has a Thick Muscularis Externa
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11
Q

What is the Anal Canal?

A
  1. It is a short (2-3cm) Canal Between the Rectum and the Anus
  2. It changes from a Proximal Simple Columnar Epithelium to a Distal Stratified Squamous Epithelium
  3. It has a Thick Muscularis Externa ( internal anal sphincter- smooth muscles)
  4. It has a Portion of Skeletal Muscle ( external anal sphincter- skeletal muscles)

the internal anal sphincter is smooth muscle, while the external anal sphincter muscle is skeletal muscle.

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12
Q

What is the name of the Thick Muscularis Externa in the Anal Canal?

A

The Internal Anal Sphincter

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13
Q

What is the name of the Skeletal Muscle in the Anal Canal?

A

The External Anal Sphincter

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14
Q

What is the Mucosal Layer of the Colon formed of?

A

Simple Columnar Epithelium

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15
Q

What is the Mucosal Layer of the Colon lined with?

A

Many Goblet Cells, in the Crypts

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16
Q

What is the function of the Goblet Cells?

A

Produce mucous, to provide Lubrication for the movement of Faeces

17
Q

Is the Circular Muscle in the Muscularis Externa of the Colon ( except rectum, anal canal and anus) Complete?

A

Yes

18
Q

Is the Longitudinal Muscle in the Muscularis Externa of the Colon Complete?

A

No

19
Q

What makes the Longitudinal Muscle of the Colon?

A

Three Bands called Teniae Coli- incomplete muscle

20
Q

What is the Teniae Coli?

A

A Tendon-Like structure which runs the entire length of the Colon

21
Q

What do the Contractions of the Teniae Coli muscle produce?

A

Haustra

22
Q

What are Haustra?

A

is a contraction that gives the Colon its puckered appearance

23
Q

What is the main function of the Colon?

A

The Dehydration of the Chyme, as it forms Faeces

24
Q

How does water get absorbed from the Chyme?

A
  1. Osmosis - through the alimentary lumen into the blood

2. Active transport of Sodium from the alimentary lumen into the blood

25
Q

What occurs due to the chyme residing for a long time in the Colon?

A

Bacterial Colonization

26
Q

What do bacteria in the Colon do?

A

Ferment Undigested Carbohydrates

27
Q

What is formed as a result of the Bacteria Fermenting Undigested Carbohydrates?

A
  1. Short Chain Fatty Acids
  2. Vitamin K
  3. Gas (Flatus)
28
Q

What happens to the Short Chain Fatty Acids and Vitamin K. formed by the Bacteria?

A

It is reabsorbed back into the blood

Vitamin K - cloting factor
Short chain fatty acid - produce energy

29
Q

What happens to the Gas (Flatus) formed by the Bacteria?

A

It is expelled through the Anus

30
Q

What normally closes the Anus?

A
  1. The Internal Anal Sphicter

2. The External Anal Sphincter

31
Q

What is the Internal Anal Sphincter made of? And what controls it?

A

Smooth Muscle controlled by the Autonomic (Parasympathetic) Nervous System

32
Q

What is the External Anal Sphincter made of? And what controls it?

A

Skeletal Muscle controlled by Somatic Fibres

33
Q

What is the Physiology of defaecation?

A
  1. An intense peritaltic wave of contraction (from the Colon to the Rectum) moves faecal matter into the Rectum
  2. This causes distention of the Rectal Wall
    and activates mechanoreceptors in the rectum, cause the Defaecation reflex
34
Q

What nerves control the Defaecation Reflex?

A

Parasympathetic Nerves via the Pelvic Splanchnic Nerve

35
Q

What is the Defaecation Reflex?

A
  1. Contraction of the Rectum
  2. Relaxation of the Internal Anal Sphincter
  3. Contraction of the External Anal Sphincter
  4. An increase in Colon Peristalsis, increasing the pressure on the External Anal Sphincter
  5. Relaxation of the External Anal Sphincter which will relax under voluntary control

GI Physiology (22 decks)

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